Structural Design of Pavements PART VI Structural ... - TU Delft

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15 Figure 8a: Graph to estimate the number of observations required at a confidence level of 95%. Figure 8b: Graph to estimate the number of observations required at a confidence level of 85%.
16 Figure 9: Placement of loading plate of FWD and geophones for load transfer measurements. Deflection measurements across the crack are important in order to be able to determine the amount of load transfer. This parameter has a significant influence on the thickness of the overlay; if there is e.g. no load transfer at all, additional maintenance work like milling and filling of the cracked area might be necessary. The magnitude of the measured deflections is dependent on the temperature, which affects the stiffness of the asphalt layers, and the moisture content, which can have a significant effect on the stiffness of the subgrade and other unbound layers. This means that if measurements are taken at various periods of the year, corrections are needed in order to be able to compare them. In order to avoid the rather complex corrections due to moisture variation, it is recommended to take the measurements in the so-called “neutral” period. During such periods the moisture content in the unbound materials is approximately at its mean level. In the Netherlands that is the late April – early May period and the October month. Because BB and LD measurements are taken at relatively low speeds, one should not perform these measurements at too high temperature levels because otherwise viscous effects will have a significant influence on the measurements which makes interpretation there-of complicated. Also the temperatures should not be too low because then the deflections might be so small that accuracy problems occur in the measurement and monitoring of the deflections. For that reason the Transport and Road Research Laboratory (TRRL) in the UK has suggested the temperature ranges shown in table 1 at which the BB and LD measurements should preferably be taken. Maximum temperature 30 o C if bitumen has a penetration lower or equal than 50 25 o C if bitumen has a penetration higher than 50 Minimum temperature 5 – 10 o C depending on the structure Table 1: Maximum and minimum temperature for deflection measurements as specified by TRRL.
Page 1 and 2: CT 4860 Structural Design of Paveme
Page 3 and 4: 2 Table of contents: Preface 3 1. I
Page 5 and 6: 4 1. Introduction: These lecture no
Page 7 and 8: 6 2. Usage and condition dependent
Page 9 and 10: 8 When a swimmer makes a nice dive
Page 11 and 12: 10 Figure 5: Principle of the autom
Page 13 and 14: 12 From the text given above it is
Page 15: 14 As shown in figure 7, 3 zones ca
Page 19 and 20: 18 5. Statistical treatment of raw
Page 21 and 22: 20 Figure 10: Results of a deflecti
Page 23 and 24: 22 Figure 12: Cumulative sum of the
Page 25 and 26: 24 Section Locations Mean SCI SD SC
Page 27 and 28: 26 6. Back calculation of layer mod
Page 29 and 30: 28 The drawn line indicates a pavem
Page 31 and 32: 30 The clayey subgrade was covered
Page 33 and 34: 32 Section I Temp Force Layer E-mod
Page 35 and 36: 34 [N] [mm] [mm] [MPa] [N] [mm] [mm
Page 37 and 38: 36 Based on these calculations, eva
Page 39 and 40: 38 8. Estimation of the remaining p
Page 41 and 42: 40 Figure 25: Load configuration us
Page 43 and 44: 42 If we assume e.g. that the defle
Page 45 and 46: 44 Figure 27: Relationship between
Page 47 and 48: 46 resistance, some parts of the pa
Page 49 and 50: 48 Log ε = 0.481 + 0.881 log SCI 3
Page 51 and 52: 50 b 3 = 1.0153 b 4 = -7.73 x 10 -6
Page 53 and 54: 52 10. Extension of the simplified
Page 55 and 56: 54 Compressive vertical strain at t
Page 57 and 58: 56 This relationship opens possibil
Page 59 and 60: 58 The remaining pavement life can
Page 61 and 62: 60 estimation of the bitumen and mi
Page 63 and 64: 62 the composition and the degree o
Page 65 and 66: 64 The life of the overlay N can si
Page 67 and 68:
66 Table 7b: Relationship between K
Page 69 and 70:
68 Figure 41: Relationship between
Page 71 and 72:
70 From the nature of the equation
Page 73 and 74:
72 σ σ t Γ ε Figure 43: Strengt
Page 75 and 76:
74 14. Effects of pavement roughnes
Page 77:
76 16. Bekker, P.C.F. Pavement perf
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Structural Design of Pavements PART VI Structural ... - TU Delft

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